That is clear. What about modifying the kickstart that yoy use in FPGA then? May we modify actual kickstart from FPGA Arcade in the way as on Apollo/Blizzard turbo cards with RemApollo/Blizkick/Loadmodule there, then to save it as custom kickstart image?

The FPGA Arcade uses standard Amiga kickstart files (like WinUAE does). You can modify and reload them any time you want, there is no limitation.